Fuel injection control method for diesel engine and regenerative control method for exhaust gas after treatment device

ABSTRACT

The present invention concerns an diesel engine fuel injection control, and a regeneration control method of exhaust gas post-treatment apparatus using this fuel injection control, and the engine fuel injection control for performing after injections (Fas, Fam) after a main injection (Fm) for activation and regeneration of the exhaust gas post-treatment apparatus, through the rising of diesel engine exhaust gas temperature or the decrease of the oxygen concentration in the exhaust gas, is composed to perform the after injections (Fas, Fam) in a range of 40° ATDC to 90° ATDC of the crank angle.  
     Whereby, the main injection can be burned, without misfire, even when the main injection is largely retarded, or, the injection quantity is increased/decreased, and the engine operation can be sustained, by keeping the engine combustion in a good state.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention concerns a fuel injection control methodfor diesel engine and a regeneration control method of exhaustpost-treatment apparatus.

[0003] More precisely, it concerns an engine fuel injection controlmethod for exhaust gas temperature rising of a diesel engine or foroxygen decrease in the exhaust gas, and a regeneration control method onan exhaust gas post-treatment apparatus such as continuous regenerationtype diesel particulate filter system of the like for purifying theexhaust gas by trapping particulate matter, using these fuel injectioncontrol methods.

[0004] 2. Detailed Description of the Prior Art

[0005] In the recent fuel injection control technology, as shown in FIG.14(a), a multistage injection technology have been developed actively byincreasing the number of injection, in order to retard the rising of theinjection quantity when starting the fuel injection, because, in theaccumulator type fuel injection apparatus of the like, in the course ofmain injection, the amount of emission of nitrogen oxides (NOxhereinafter) or particulate matter (PM: particulate: PM hereinafter)increases, if it is injected at once, as the rate of injection inrespect to the crank angle is high from the beginning, the amount offuel to be injected into the combustion chamber increases suddenly, andthe fuel blows in at a stretch.

[0006] Besides, a fuel injection control technology has been developedfor performing an after injection with a small interval after the maininjection, and accelerating the mixture of fuel injected in the maininjection and sucked air, by intermediated of the energy of this afterinjection, as shown in FIG. 14(b), in order to early terminate thecombustion of fuel of the main injection and thereby reduce PM.

[0007] In addition, the fuel injection mode control method of Japanesepatent application Kokai publication No. 2000-97077 proposes to improvethe ignitionability of the fuel injection, by adopting a multistageinjection mode for performing a multistage pilot injection, as shown inFIG. 14(c), during the engine start.

[0008] These fuel injection control technologies aim at reducing theemission of NOx and PM, terminating the fuel combustion rapidly, andconverting the thermal energy into engine output as much as possible, asa result, the exhaust gas temperature lowers.

[0009] On the other hand, as for the diesel engine, in recent years, anexhaust gas post treatment apparatus provided with oxide catalyst andNOx catalyst for elimination of hazardous constituents such as PM, NOx,SOx and others emitted from the engine and further a diesel particulatefilter (DPF for Diesel Particulate Filter: PDF hereinafter) for catchingPM is arranged in an exhaust passage.

[0010] The filter for directly catching this PM includes ceramicmonolithic honeycomb shape wall flow type filters, fiber shape typefilters where ceramics or metals are formed into fiber, or others, antthe exhaust gas purification apparatus using these DPF are installed inthe middle of the engine exhaust pipe, cleans and emits the exhaust gas.

[0011] However, this filter for catching PM is clogged along the trap ofPM, and the exhaust gas pressure (exhaust gas pressure) rises as thetrapped amount of PM increases, it is required thereby to eliminate PMfrom this DPF, and therefore, several methods and systems have beendeveloped.

[0012] Among them, there is a system for eliminating PM by combustionthrough the heating of the filter with an electric heater or a burner,or back washing by flowing the air in the opposite direction; however,in the case of these systems, the fuel efficiency deteriorates, becausePM is burned by supplying heating energy from outside, and theregeneration control is difficult.

[0013] In addition, in the case of adopting these systems, often twolines of exhaust passage provided with DPF are installed, PM trap andfilter regeneration are repeated alternately, thereby tending toincrease the size and cost of the system.

[0014] In order to cope with these problems, a continuous regenerationtype DPF system as shown in FIGS. 15 to 17 have been proposed.

[0015]FIG. 15 shows an example of continuous regeneration type DPFsystem (NO₂ regeneration type DPF system) by intermediate of nitrogendioxide (NO₂, hereinafter), and this continuous regeneration type DPFsystem 1A is composed of a wall flow type filter 3Ab and a oxidationcatalyst 3Aa disposed upstream thereof. This upstream side oxidationcatalyst 3Aa carrying platinum or the like oxidizes nitrogen monoxide(NO, hereinafter) in the exhaust gas to obtain NO₂ (2NO+O₂->2 NO₂) andthis N0 ₂ oxidizes PM caught by the downstream side filter 3Aa toobtain, carbon dioxide (CO₂, hereinafter) (2 NO₂+C->2NO+CO₂) removingthereby PM.

[0016] Such this oxidation of PM by NO₂ is performed with less energybarrier and at a lower temperature than the oxidation of PM by oxygen(O₂, hereinafter), and thereby, with a reduced external energy supply,the filter can be regenerated by removing PM through oxidation, all theway trapping PM continuously by using thermal energy in the exhaust gas.

[0017] Besides, the continuous regeneration type DPF system (integratedNO₂ regeneration type DPF system) 1B shown in FIG. 16 is an improvementof the system 1A shown in FIG. 15, ,in which oxidation catalyst 32A isapplied on the wall surface of a filter 3B provide with wall flow typecatalyst, and the oxidation of NO in the exhaust gas and the oxidationof PM by NO₂ are performed on this wall surface. Thereby, the system issimplified.

[0018] Then, the continuous regeneration type DPF system (DPF systemprovided with PM oxidation catalyst) 1C shown in FIG. 17 appliesprecious metal oxidation catalyst 32A such as platinum (Pt) or the likeand PM oxidation catalyst 32B to the wall surface of a filter 3C providewith wall flow type PM oxidation catalyst, and the oxidation of PM isperformed on this wall surface from a lower temperature.

[0019] This PM oxidation catalyst 32B is a catalyst for direct PMoxidation by means of O₂ in the exhaust gas, composed of cerium dioxide(CeO₂) or the like.

[0020] For this continuous regeneration type DPF system 1C, PM isoxidized by NO₂ using mainly a reaction of the oxidation catalyst 32A tooxidize NO to NO₂ in a low temperature oxidation range (about 350° C. to450° C.), PM is oxidized by a reaction of the PM oxidation catalyst 32Bto oxidize directly PM by means of O₂ in the exhaust gas(4CeO₂+C→2Ce₂O₃+CO₂, 2Ce₂O₃+O₂→4Ce O₂ or others) in a middle temperatureoxidation range (about 400° C. to 600° C.), while PM is oxidized by O₂in the exhaust gas in a high temperature oxidation range (600° C. ormore) higher than the temperature of PM combustion by O₂ in the exhaustgas.

[0021] These continuous regeneration type DPF systems oxidize andeliminate PM while catching PM, by lowering PM oxidation temperaturethrough the use of PM oxidation by catalyst or nitrogen dioxide.

[0022] However, even in these continuous regeneration type DPF systems,it is still necessary to rise the exhaust gas temperature to the orderof 350° C., and the aforementioned reaction does not occur, and thefilter can not be regenerated by PM oxidation in an engine operationstate with a low exhaust gas temperature such as idling operation,extremely low load operation or the like, and PM continues to beaccumulated in the filter, causing the problem of filter clogging.

[0023] For instance, in the idling operation, low speed or extremely lowload operation when the engine break is operated on the downhill, thefuel is burned scarcely, a low temperature exhaust gas flows into thecontinuous regeneration type DPF apparatus, lowering the catalysttemperature and deteriorating the catalyst activity.

[0024] If the idling or extremely low load engine operation issustained, PM trap progresses without supply of a hot exhaust gas thatcan oxidize and eliminate PM; therefore, PM can not be oxidized andeliminated while PM trap continues, resulting in the progress of filterclogging.

[0025] This progress of filter clogging increases the exhaust gaspressure and deteriorates the fuel efficiency and, moreover, when theexhaust gas pressure rises excessively along with the progress of filterclogging, the engine will stop, and if things come to the worst, it willdevelop to the disability of restart.

[0026] Especially, in the case of using a vehicle loaded with thiscontinuous regeneration type DPF system for a home delivery service orthe like dominated by the an urban area traveling, the engine runsmainly with a low exhaust gas temperature; therefore, it is oftennecessary to control in order to rise the exhaust gas temperature.

[0027] Therefore, it is planned to rise the exhaust gas temperature byretarding the injection timing, in the engine fuel injection; however, amisfire of injected fuel may be provoked if it is tried to rise theexhaust gas temperature by retarding considerably the injection timing,a limit occurs in the injection timing retarding angle, leading to theoccurrence of a limit for the exhaust gas temperature rising, and therange of possible temperature rising comes to be reduced.

[0028] In addition to the regeneration of the filter for burning andeliminating PM caught in the aforementioned DPF, it comes to be requiredto rise, even momentarily, the exhaust gas temperature withoutincreasing the engine output, or to generate temporally an exhaust gasof reducing atmosphere by deducing the oxygen concentration in theexhaust gas to almost zero, in order to activate by increasing thetemperature of oxidation catalyst and NOx catalyst used for exhaust gascountermeasures, or to regenerate the occlusion substance of NOxocclusion reduction type catalyst.

[0029] In short, even temporally, a fuel injection control contrary, asthe result, to the fuel injection control for lowering the exhaust gastemperature, by burning the fuel injected into the combustion chamber assoon as possible for increasing the engine output, as required in theprior art, comes to be required.

[0030] As one of methods for increasing the exhaust gas temperature andlowering the oxygen concentration, there is a method for retarding(delay) the main injection. In this retard of main injection, the morethe timing is retarded, in short, the larger is the retard amount, theless the energy of the injected fuel is concerted in the engine output,and the more rises the exhaust gas temperature. Moreover, oxygenconcentration in the exhaust gas can be reduced by increasing the fuelinjection amount during the main injection.

[0031] In this retard of main injection, as the main injection which isgenerally performed neat the top dead center (TDC) is retarded, thepressure and temperature lower along with the distance from the TDC,only with the main injection, making the ignitionability difficult; inorder to avoid this problem, a pilot injection is made near the TDCwhere the pressure and temperature are high, this fuel is burned tosecure a kindling charcoal, so that the fuel of the main injection burnssecurely.

[0032] Nevertheless, concerning this main injection retard, there areproblems of misfire, deterioration in output torque and fuel efficiencyas explained below.

[0033] Concerning the misfire, it comes to be demanded to prolong thecombustion time as long as possible, by increasing the interval betweenthe pilot injection and the main injection that was not required for theprior art, in the retard of main injection, and misfire occurs if it isintended to increase the retard amount of the main injection, simply byan injection control only with the pilot injection and the retard ofmain injection, to meet with this demand.

[0034] Moreover, there is a case where the injection quantity is reducedin order to intend to optimize the main injection quantity in respect tothe required exhaust gas temperature, in order to improve the fuelefficiency, the kindling charcoal becomes insufficient and flames off ifthe pilot injection quantity of that moment is constant.

[0035] Because of these problems of misfire, a limit is developed in therising of exhaust gas temperature, and, the decrease of the oxygenconcentration becomes unable to be achieved.

[0036] Also, as for torque output, when this retard control of maininjection is performed, the engine output torque lowers as thecombustion of the main injection is delayed, making impossible tomaintain a high output torque, so there is a problem that this retardcontrol of main injection can not be used in the case of desiring tomaintain an output torque.

[0037] There, concerning the retard operation of this main injection,Japanese Patent Application No. 2000-291462 performs an auxiliaryinjection only once (second injection pattern), when the injectiontiming of the main injection is retarded largely, for increasing theexhaust temperature, and thereby the misfire is prevented.

[0038] Howsoever, if it is tried to maintain a combustion flame untilthe timing when the main injection is injected, only by a single subinjection, it becomes necessary to increase the fuel injection quantityin this sub injection, causing the problem of fuel efficiencydeterioration.

[0039] At the same time, torque is generated by this sub injection,deteriorating the drivability. Moreover, a single sub injection limitsthe retard amount of the main injection, and the rising range of exhausttemperature will be reduced disadvantageously.

SUMMARY OF THE INVENTION

[0040] The present invention has been devised in order to resolve theaforementioned problems and has an object to provide a diesel enginefuel injection control method allowing to activate and regenerate theexhaust gas post-treatment apparatus, by increasing the exhaust gastemperature or lowering the oxygen concentration in the exhaust gas,through the fuel injection control, in the fuel injection of a dieselengine.

[0041] Another object is to provide a regeneration method for continuousregeneration type DPF system, allowing to rise the exhaust gastemperature, oxidize and eliminate PM, through the engine fuel injectioncontrol, even during an engine operation state with a low exhaust gastemperature such as idling operation, extremely low load operation orthe like, in a continuous regeneration type DPF system.

[0042] The diesel engine fuel injection control method for achieving theaforementioned objects is a fuel injection control for performing anafter injection after the main injection, composed as follows.

[0043] 1) A desel engine fuel injection control for performing an afterinjection after the main injection for at least one of rising of dieselengine exhaust gas temperature and decrease of the oxygen concentrationin the exhaust gas, in which the after injection is performed in a rangeof 40° ATDC to 90° ATDC of the crank angle.

[0044] In short, the exhaust gas temperature is risen by trailing thecombustion and taking the combustion heat into the exhaust gas, throughthe execution of after injection with an ATDC crank angle lager than thenormal after injection, corresponding to the range of 40° to 90°obtained experimentally in terms of crank angle after the passage of thetop dead center TDC (ATDC).

[0045] The exhaust gas temperature can be risen by performing this afterinjection after the main injection, and also, the oxygen concentrationin the exhaust gas can be lowered.

[0046] Consequently, in an exhaust gas post-treatment apparatus to bedisposed on the lower side of this diesel engine, oxidation catalyst andNOx catalyst can be activated or regenerated, and the filter can beregenerated by burning and eliminating PM trapped by the DPF.

[0047] 2) The aforementioned diesel engine fuel injection controlmethod, ,in which the after injection is performed by a multistageinjection of sub after injection and main after injection and, at thesame time, the sub after injection is performed in a range of 40° ATDCto 70° ATDC of the crank angle and the main after injection in a rangeof 70° ATDC to 90° ATDC of the crank angle.

[0048] By inserting a sub after injection between this main injectionand a main after injection and performing in a sub after injection rangeof 40° to 70° and a main after injection range of 70° to 90° , thekindling fire can be maintained until the main after injection and themain after injection can be burned without misfire, even when the timingof main after injection is largely retarded than the top dead centerTDC, permitting to create an exhaust gas state necessary forregeneration of catalyst or others. These ranges are obtainedexperimentaly.

[0049] 3) The aforementioned diesel engine fuel injection controlmethod, in which the main after injection is performed by calculatingthe injection quantity and the injection timing of the main afterinjection according to the relation of the injection quantity and theinjection timing of the main after injection in respective operationstates of an engine, determined previously.

[0050] The injection data of this main after injection includes, forexample, map data MVam (Q,Ne), MTam (Q, Ne) in respect of torque Q andengine speed Ne indicating respective operation states of an engine, orothers, determined preliminarily by experiment or computation, and inputpreviously into a control apparatus for performing this injectioncontrol.

[0051] According to this composition, an appropriate main afterinjection can be realized by a relatively simple algorism, because theafter injection control can be performed by selecting appropriateinjection quantity and injection timing of the main after injection.

[0052] 4) The aforementioned diesel engine fuel injection controlmethod, in which the sub after injection is performed by calculating theinjection quantity and the injection timing of the sub after injectionaccording to the relation of the injection quantity and the injectiontiming of the sub after injection in respective operation states of anengine, determined previously.

[0053] The data of injection quantity and injection timing of this subafter injection includes, for example, map data MVas (Q,Ne), MTas (Q,Ne) in respect of torque Q and engine speed Ne indicating respectiveoperation states of an engine, or others, similarly to the data ofinjection quantity and injection timing of the main after injection,determined preliminarily by experiment or computation, and inputpreviously into a control apparatus for performing this injectioncontrol.

[0054] It should be noted that information data whether to perform ornot the sub after injection can be included by setting MVas (Q, Ne)=0 inthe range without sub after injection, and in the case of setting all tozero, the after injection control is set to not to perform the sub afterinjection.

[0055] According to this composition, the fuel of the main afterinjection can be burned efficiently, all the way saving the fuel, by arelatively simple algorism, because the after injection control can beperformed by selecting appropriate injection quantity and injectiontiming of the sub after injection.

[0056] 5) The diesel engine fuel injection control method, in which itis determined whether to perform or not the sub after injection, basedon the output values of a fuel combustion state detection means, all theway monitoring the fuel combustion state in the engine combustionchamber by the fuel combustion state detection means, and the sub afterinjection is performed based on the determination.

[0057] As for this fuel combustion state detection means for monitoringthe fuel combustion state in the engine combustion chamber, there is anion gap sensor. This ion gap sensor uses the generation of electron bythe combustion of a fuel, such as HC or others and can monitor thecombustion state as electric resistance variation, by applying a voltageof about 50 to 200V to a conductive portion facing to the inside of thecombustion chamber and separated by an appropriate interval (forinstance, about 1 mm) and take the generation of electron by thiscombustion as electric resistance variation, by detecting the electricresistance variation of this conductive portion.

[0058] In short, when the fuel of main injection has burned out and thefuel of main after injection does not ignites, the ion concentrationdecreases and the resistance increases when the fuel of main injectionburns out, it will be enough to perform the sub after injection bydetecting this resistance variation, and in case where the ionconcentration is high and the resistance decreases, the sub afterinjection shall not be performed.

[0059] According to this composition, the main after injection can beburned, securely, because it is determined whether to perform or not thesub after injection, by monitoring the fuel combustion state in thecombustion chamber.

[0060] 6) The diesel engine fuel injection control method, in which atleast one of injection quantity and injection timing of the sub afterinjection is adjusted and controlled, based on the output values of afuel combustion state detection means, all the way monitoring the fuelcombustion state in the engine combustion chamber by the fuel combustionstate detection means.

[0061] In short, the feedback control is realized by taking the outputof the ion gap sensor which is a fuel combustion state detection meansas desired value and at least one of injection quantity and injectiontiming of the sub after injection as control variable.

[0062] According to this composition, the main after injection can beburned by performing an optimal sub after injection control, and itbecomes possible to realize the after injection control, all the waylimiting the fuel consumption to the strict minimum.

[0063] In addition, for the diesel engine fuel injection control methodto achieve the object, the relation between the pilot injection and themain injection is composed as follows.

[0064] 7) An diesel engine fuel injection control method for performinga pilot injection and a main injection by controlling the fuel injectionof a diesel engine, and for performing at least one engine fuelcombustion among retard of the main injection or increase/decrease ofthe injection quantity, for at least one of rising of diesel engineexhaust gas temperature and decrease of the oxygen concentration in theexhaust gas, in which the injection quantity of the pilot injection isincreased/decreased, in accordance with the increase/decrease of retardamount and injection quantity of the main injection.

[0065] The increase/decrease of retard amount and injection quantity ofthis main injection is not constant for a normal operation, but shall beperformed for rising the exhaust gas temperature without increasing theengine output, or for enriching the exhaust gas composition, only duringthe activation of oxidation catalyst of the exhaust gas post-treatmentapparatus, or the regeneration treatment of NOx catalyst or DPF filter.

[0066] There, the main injection can be burned without misfire, evenwhen the main injection is injected with a large retard amount, by theincrease/decrease of injection quantity in the pilot injection, inaccordance with the increase/decrease of retard amount of this maininjection, allowing to secure an exhaust gas composition and atemperature necessary for catalyst regeneration or others.

[0067] In addition, the main injection can be burned without misfire,even when the injection quantity of main injection is reduced, by theincrease/decrease of injection quantity in the pilot injection, inaccordance with the increase/decrease of injection quantity of this maininjection, allowing to secure an exhaust gas composition and atemperature necessary for catalyst regeneration or others.

[0068] 8) The aforementioned diesel engine fuel injection controlmethod, in which the injection quantity of the pilot injection iscalculated in accordance with the relation between at least one quantityamong the retard amount or the injection quantity of the main injectionobtained previously and the injection quantity of the pilot injection.

[0069] According to this composition, the injection quantity of thepilot injection can be increased/decreased in accordance with the retardamount, injection quantity of the main injection by a relatively simplealgorism, because it increases/decreases in accordance with the retardamount, injection quantity of the main injection, according to arelation determined preliminarily by experiment or others.

[0070] In addition, as the injection quantity of the pilot injectionincreases/decreases in accordance with the retard amount, injectionquantity of the main injection, the fuel will not be consumedunnecessarily allowing to save the fuel compared to the case of simpleincrease of the pilot injection quantity, and the increase of fuelconsumption can be limited to the minimum.

[0071] It should be noted that this increase/decrease quantity can notbe determined uniformly and can be obtained by experiment for respectivekind of engines, because the injection quantity of the pilot injectionincreases along with the increase of the retard amount of the maininjection, and the injection quantity of the pilot injection decreasesalong with the increase of the injection quantity of the main injection,but the actual increase/decrease quantity varies according to the kindof engine, or others.

[0072] 9) Or, the diesel engine fuel injection control method, in whichthe injection quantity of the pilot injection is increased/decreasedbased on the output value of a fuel combustion state detection means,all the way monitoring the fuel combustion state in the enginecombustion chamber by the fuel combustion state detection means, when alleast one of the retard amount and the injection quantity of the maininjection shall be increased/decreased.

[0073] As for this fuel combustion state detection means for monitoringthe fuel combustion state in the engine combustion chamber, theaforementioned ion gap sensor can be used, and the pilot injection canbe performed with an optimal injection quantity through the feedbackcontrol, by taking the output (current value) of this ion gap sensor asdesired value, and the injection quantity of the pilot injection ascontrol variable.

[0074] Consequently, the main injection can be burned securely with astrict minimum necessary injection quantity of the pilot injection.Besides, it becomes unnecessary to determine the relation between theretard amount, injection quantity of the main injection and theinjection quantity of the pilot injection, preliminarily, by experimentor others.

[0075] Also, the diesel engine fuel injection control method forachieving the object is composed as follows, including the retard of themain injection and twice or more sub injections.

[0076] 10) It is composed to retard the injection timing of the maininjection and, at the same time, perform the sub injection twice or moreat a timing before the injection timing of the main injection, in orderto rise the exhaust temperature of a diesel engine, the first injectionof the sub injection is performed at a timing allowing theignitionability, and the combustion flame is sustained until theinjection timing of the main injection, by the second and followinginjections of the sub injection.

[0077] 11) Then, the injection timing of the main injection is set to25° ATDC to 45° ATDC, so that a hotter exhaust gas can be obtained, bythis diesel engine fuel injection control method. The exhausttemperature can be risen considerably (for instance, about 200° C.), bythis considerable retard of the injection timing of the main injection.

[0078] This injection timing of the main injection, 25° ATDC, is thelower limit value where the effect of the multistage auxiliary injectioncan be deployed, while the upper limit value 45° ATDC is a boundarywhere the substantial effect begins to be abated in view of the fuelefficiency.

[0079] 12) And, concerning the sub injection of this diesel engine fuelinjection control method, the exhaust temperature can be risen withoutincreasing the torque, and the variation due to the torque generated inthe normal operation (operation for generating desired engine speed andtorque, without considering specifically the exhaust temperature) can besuppressed, by increasing consecutively the fuel injection quantity ofthe sub injection of retarded injection timing more than the fuelinjection quantity of the sub injection of an earlier injection timing.

[0080] The relation between the number of times, injection timing, andinjection quantity of this sub injection, the retard amount of theinjection timing of the main injection, and the rising amount of theexhaust temperature can be determined by experiment, the data obtainedby this experiment are stored in a fuel injection control apparatus inthe form of map date or the like, and this fuel injection control can beperformed easily, by determining the injection control value of the subinjection and the main injection from this data, as necessary, when thisfuel injection control is performed.

[0081] Consequently, according to this diesel engine fuel injectioncontrol method, the main injection can be retarded considerably and theexhaust temperature can be risen considerably, because the combustionflame in the cylinder can be maintained, all the way generating ageneration torque identical to the torque generated in the normaloperation, by suppressing the generation of torque variation, throughthe control of the injection quantity and the injection timing ofmultiple times of sub injections.

[0082] Then, the aforementioned fuel injection control method can beused by integrating into a regeneration control method of an exhaust gaspost-treatment apparatus such as continuous regeneration type DPFsystem.

[0083] The regeneration control method of exhaust gas post-treatmentapparatus is composed by including the aforementioned diesel engine fuelinjection control method in the regeneration control to be performed forregeneration treatment of an exhaust gas post-treatment apparatus, inthe exhaust gas post-treatment apparatus for excluding hazardousconstituent in the engine exhaust gas.

[0084] According to this regeneration control method, the exhaust gaspost-treatment apparatus can be activated or regenerated by increasingthe exhaust gas temperature, or decreasing the oxygen concentration inthe exhaust gas, during the regeneration of oxidation catalyst, NOxcatalyst, occlusion substance of NOx occlusion reduction type catalyst,and DPF for catching PM of the exhaust gas post-treatment apparatus tobe arranged at the lower side on a diesel engine.

[0085] In addition, the regeneration control method of exhaust gaspost-treatment apparatus of the present invention have the followingeffects when the exhaust gas post-treatment apparatus is a continuousregeneration type diesel particulate filter system having a filter forcatching particulate in the engine exhaust gas, and oxidizing andeliminating the caught particulate matter by the catalytic function.

[0086] The use of the aforementioned injection control method permits toregenerate the filter through the oxidation and elimination of PMaccumulated in the filter, by rising the exhaust gas temperature, evenif the filter regeneration comes to be required in an engine operationstate difficult for the filter regeneration by the oxidation of PM dueto low exhaust gas temperature, such as idling operation, extremely lowload operation or the like.

[0087] Further, the filter can be regenerated without deterioration ofthe drivability, because the exhaust temperature can be risen,suppressing the variation from the engine speed and torque in the normalengine operation before starting the regeneration.

[0088] Therefore, the rising of exhaust gas pressure can be controlled,because the filter can be regenerated any time. Consequently, generationof engine stole or other inconveniences due to the exhaust pressurerising can be avoided. Furthermore, as excessive accumulation of PM canbe avoided, the filter melting damage which occurs easily during the PMoxidation following this excessive accumulation of PM can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0089]FIG. 1 is a diagram showing the relation between pilot injection,main injection, sub after injection and main after injection, in thefuel injection control of a first embodiment, (a) shows the normal fuelinjection before the after injection, (b) shows the after injectioncomprising only a main after injection in the case of no sub afterinjection, and (c) shows the sub after injection and the main afterinjection.

[0090]FIG. 2 is a diagram showing the relation between the injectiontiming of the after injection and the exhaust gas temperature;

[0091]FIG. 3 is a diagram showing the relation between the injectiontiming of the sub after injection and the main after injection and theexhaust gas temperature, in the case of fixing the injection timing ofthe sub after injection and changing the injection timing of the mainafter injection;

[0092]FIG. 4 is a diagram showing the relation between the injectiontiming of the sub after injection and the main after injection and theexhaust gas temperature, in the case of fixing the injection timing ofthe main after injection and changing the injection timing of the subafter injection;

[0093]FIG. 5 is a diagram showing the relation between pilot injectionand main injection, in the fuel injection control of a secondembodiment, (a) shows the injection before retarding the main injection,(b) shows the injection in the case of small retard of the maininjection, and (c) shows the injection in the case of large retard ofthe main injection;

[0094]FIG. 6 is a diagram showing the relation between pilot injectionand main injection, in the fuel injection control of a third embodiment,(a) shows the injection before increasing/decreasing the injectionquantity of the main injection, (b) shows the injection in the case ofincreased injection quantity of the main injection, and (c) shows theinjection in the case of decreased injection quantity of the maininjection;

[0095]FIG. 7 is a schematic illustration showing an example of fuelinjection control of a fourth embodiment;

[0096]FIG. 8 is a schematic illustration showing another example of fuelinjection control of the fourth embodiment;

[0097]FIG. 9 is a composition diagram of a continuous regeneration typeparticulate filter system of an embodiment according to the presentinvention;

[0098]FIG. 10 is a schematic composition diagram of a filter withcatalyst of an embodiment according to the present invention;

[0099]FIG. 11 is a flow chart showing a regeneration control method of acontinuous regeneration type particulate filter system of an embodimentaccording to the present invention;

[0100]FIG. 12 is a diagram showing an example of fuel injection controlwith multistage auxiliary injection of fourth embodiment according tothe present invention;

[0101]FIG. 13 is a diagram showing a comparative example of fuelinjection control with pilot injection of the prior art;

[0102]FIG. 14 is a diagram showing an example of fuel injection in theprior art, (a) shows an example of multistage injection, (b) shows anexample of after injection, and (c) shows the pilot injection of themultistage injection mode;

[0103]FIG. 15 is a composition diagram showing an example of acontinuous regeneration type DPF system provided with oxidation catalystof the prior art;

[0104]FIG. 16 is a composition diagram showing an example of acontinuous regeneration type DPF system provided with a filter withoxidation catalyst of the prior art; and

[0105]FIG. 17 is a composition diagram showing an example of acontinuous regeneration type DPF system provided with a filter with PMoxidation catalyst of the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0106] Now, embodiments of the diesel engine fuel injection controlmethod and the regeneration control method of continuous regenerationtype DPF system according to the present invention shall be describedbased on drawings.

[0107] The first embodiment of the diesel engine fuel injection controlmethod concerns the after injection, the second embodiment the injectionquantity of the pilot injection and the retard of the main injection,the third embodiment the injection quantity of the pilot injection andthe injection quantity of the main injection, and the fourth embodimentthe main injection and the multistage auxiliary injection.

[0108] First Embodiment

[0109] First, the diesel engine fuel injection control method of thefirst embodiment concerning the after injection shall be described.

[0110] In this diesel engine fuel injection control method, pilotinjection Fp and main injection Fm as shown in FIG. 1(a) are performedduring the normal operation. The injection quantity of this pilotinjection Fp is a prescribed value and, a previously established fixedquantity.

[0111] There, the after injection is performed when it becomes necessaryto rise the exhaust gas temperature, or, generate temporally an exhaustgas of reductive atmosphere by lowering the oxygen concentration in theexhaust gas, in order to activate the oxidation catalyst, regenerateabsorption/occlusion substance of NOx occlusion reduction type catalyst,or regenerate the filter by burning and eliminating PM caught by theDPF.

[0112] For this after injection, in order to make the oxygenconcentration in the exhaust gas and the exhaust gas temperature thepredetermined desired value, the fuel injection is controlled withpreviously established injection quantity Vam and injection timing Tamof the main after injection Fam, or the oxygen concentration and theexhaust gas temperature are detected by an oxygen concentration sensor,an temperature sensor or others, the injection quantity Vam andinjection timing Tam of the main after injection Fam are modified by thefeedback control, and the main after injection Fam is performed withthus obtained optimal injection quantity Vam and injection timing Tam.

[0113] There, in case where it is possible to secure the combustion byan after injection comprising only the main after injection Fam, asshown in FIG. 1(b), this main after injection Fam is performed in arange of 40° ATDC to 90° ATDC of the crank angle. Namely, the afterinjection is performed in the range of 40° to 90° of the crank angleafter passing through the top dead center TDC (ATDC).

[0114] The range of 40° ATDC to 90° ATDC for the after injectioncomprising only the main after injection Fam is the one determined byexperiment. In short, as shown in FIG. 2, it is determined from therange where the exhaust gas temperature becomes high when the injectiontiming of the main after injection (after injection) Fam is changed,respectively, in the case of high engine speed operation (A) and in thecase of low engine speed operation (B) for the engine operation state.

[0115] This high engine speed means an engine speed equal or superior tothe engine speed generating the maximum torque called “torque point”,and the low engine speed an engine speed equal or inferior to thistorque point. The idling operation is included in this low engine speed.This torque point may depend on the kind of engine, but, for instance,is an engine speed of about 2500 rpm.

[0116] Besides, in case where the combustion can not be secured only bythis single main after injection Fam, the after injection is performedin two-stage injection comprising a sub after injection Fas and a mainafter injection Fam, as shown in FIG. 1(c), and the sub after injectionFas is performed in a range of 40° ATDC to 70° ATDC of the crank angleand the main after injection Fam is performed in a range of 70° ATDC to90° ATDC of the crank angle. It should be noted that the injectionquantity Vas of this sub after injection Fas is on the order of about 5%to 50% of the injection quantity Vam of main after injection Fam.

[0117] This range of injection timing 70° ATDC to 90° ATDC for the mainafter injection Fam is the one determined by experiment, and isdetermined from the range where the exhaust gas temperature becomes highwhen the injection timing of the main after injection Fam is changed, byoperating with the sub after injection Fas fixed to the predeterminedvalue of 40° ATDC to 70° ATDC.

[0118]FIG. 3 shows respective exhaust gas temperatures when theinjection timing of the main after injection Fam is changed, in the caseof operating with the sub after injection Fas fixed to the predeterminedvalue of 40° ATDC (C) and in the case of operation by fixing at to 70°ATDC (D). A range of this FIG. 3 where the exhaust gas becomes hot (70°to 90°) is selected and taken as the injection timing of the main afterinjection Fam.

[0119] Now, the range of 40° to 70° ATDC for the sub after injection Fasis also the one determined by experiment, and is determined from therange where the exhaust gas temperature becomes high when the injectiontiming of the sub after injection Fas is changed, in the case of settingthe main after injection Fa to a predetermined value in the range of 70°ATDC to 90° ATDC. FIG. 4 shows the exhaust gas temperature when theinjection timing of the sub after injection Fas is changed (E), in thecase of setting the main after injection Fam to a predetermined value inthe range of 70° ATDC to 90° ATDC. A range of this FIG. 4 where theexhaust gas becomes hot (40° to 70°) is selected and taken as theinjection timing of the sub after injection Fas.

[0120] A variety of methods exist for injection control of these subafter injection Fas and main after injection Fam, and two of them shallbe described below.

[0121] In the first method, the after injection Fas, Fam is performed asfollows.

[0122] First, the injection quantity Vam and the injection timing Tam ofthe main after injection Fam are calculated from map data MVam (Q,Ne),MTam (Q, Ne) or others, showing the relation between the injectionquantity Vam and the injection timing Tam of the main after injectionFam in respect of torque Q and engine speed Ne indicating respectiveoperation states of an engine, determined preliminarily. These map dataMVam, MTam or others are data determined preliminarily by experiment orcomputation, and input previously into a control apparatus forperforming this injection control.

[0123] This allows to control the after injection by selectingappropriate injection quantity Vam and injection timing Tam of the mainafter injection Fam and, thereby, to perform an appropriated main afterinjection Fam by a relatively simple algorism.

[0124] Also, the injection quantity Vas and the injection timing Tas ofthe sub after injection Fas are calculated from map data MVas (Q,Ne),MTas (Q, Ne) or others, showing the relation between the injectionquantity Vas and the injection timing Tas of the sub after injection Fasin respect of torque Q and engine speed Ne indicating respectiveoperation states of an engine, determined preliminarily. These map dataMVas, MTas or others are data determined preliminarily by experiment orcomputation, and input previously into a control apparatus forperforming this injection control.

[0125] It should be noted that information data whether to perform ornot the sub after injection Fas can be included by setting MVas (Q,Ne)=0 in the range without performing the sub after injection Fas, andin the case of setting all to zero, the after injection control is setto not to perform the sub after injection Fas.

[0126] According to this composition, the fuel of the main afterinjection Fam can be burned efficiently by performing the sub afterinjection Fas efficiently, all the way saving the fuel, by a relativelysimple algorism, because the after injection control can be performed byselecting appropriate injection quantity Vas and injection timing Tas ofthe sub after injection Fas.

[0127] In addition, here, though the injection quantity Vas and theinjection timing Tas of the sub after injection Fas are determined forrespective engine operation states (Q, Ne), it can also be composed todetermine for the injection quantity Vam and injection timing Tam of themain after injection Fam. In this case, the map data will take a formatof MVas2 (Vam, Tam), MTas2 (Vam, Tam).

[0128] Also, the second method is performed similarly to the firstmethod concerning the injection control of the main after injection Fam.

[0129] In other words, the injection quantity Vam and injection timingTam of the main after injection Fam are computed according to therelation of the injection quantity MVam (Q, Ne) and the injection timingMTam (Q, Ne) of the main after injection Fam are determined inrespective engine operation states.

[0130] Then, in this second method, a voltage of about 50 to 200V isapplied to a conductive portion facing to the inside of the combustionchamber and separated by an appropriate interval (for instance, about 1mm), and an ion gap sensor for detection of electric resistance of thisconductive portion is installed to monitor the fuel combustion state inthe engine combustion chamber.

[0131] All the way monitoring the fuel combustion state in the enginecombustion chamber by this ion gap sensor, it is judged whether toperform or not the sub after injection Fas, based on the output value ofthis ion gap sensor, and the sub after injection Fas is performed basedon this judgment. In short, it is composed to perform the sub afterinjection Fas if the output of the ion gas sensor exceeds apredetermined judgment value, and not to perform the sub after injectionFas if the output of the ion gas sensor does not exceed thepredetermined judgment value.

[0132] To be more precise, it is so controlled to perform the sub afterinjection Fas when the ion concentration lowers after the main injectionFm and the electric resistance exceeds the predetermined judgment value,as the fuel of the main injection Fm has burned out and the fuel of themain after injection Fam becomes hard to ignite and, on the contrary,not perform the sub after injection Fas when the ion concentration ishigh and the electric resistance is lower than the predeterminedjudgment value, as the combustion of the main injection Fm is sustainedand the fuel of the main after injection Fam can ignite easily.

[0133] Furthermore, the feedback control is realized by taking theoutput of this ion gap sensor as desired value and at least one ofinjection quantity Vas and injection timing Tas of the sub afterinjection Fas as control variable. It should be appreciated that, inthis case, the other not taken as control value shall be predeterminedfixed quantity.

[0134] In short, when the injection quantity Vam and injection timingTam of the main after injection Fam are determined, the main afterinjection Fam is performed with this injection quantity Vam andinjection timing Tam and, at the same time, the sub after injection Fasis performed with the injection quantity Vas and injection timing Tasthrough this feedback fcontrol. Thereby, it is so composed toincrease/decrease automatically at least one of injection quantity Vasand injection timing Tas of the sub after injection Fas.

[0135] In the case of using this ion gap sensor, it is unnecessary todetermine, previously, injection quantity Vas and injection timing Tasof the sub after injection Fas corresponding to the engine operationstate or the injection timing Tam of the main after injection Fam,allowing also to burn the fuel of the main after injection Fam securely.

[0136] Moreover, being feedback control, the injection quantity Vas ofthe sub after injection Fas can be limited to the strict minimum,allowing to save more fuel.

[0137] Second Embodiment

[0138] In the diesel engine fuel injection control method of the secondembodiment concerning the injection quantity of the pilot injection andthe retard of the main injection, pilot injection Fp and main injectionFm as shown in FIG. 5(a) are performed during the execution of thenormal pilot injection. The injection quantity of this pilot injectionFp is a prescribed value and, a previously established fixed quantity.

[0139] There, the retard of the main injection Fm is increased/decreasedwhen it becomes necessary to rise the exhaust gas temperature, or,generate temporally an exhaust gas of reductive atmosphere by loweringthe oxygen concentration in the exhaust gas, in order to rise thecatalyst temperature of the exhaust gas post-treatment apparatus,regenerate NOx occlusion reduction type catalyst, or regenerate thefilter by burning and eliminating PM caught by the DPF.

[0140] For this retard of the main injection Fm, in order to make theoxygen concentration in the exhaust gas and the exhaust gas temperaturethe predetermined desired value, the main injection FM is performed by apreviously established retard amount Rm, or the oxygen concentration andthe exhaust gas temperature are detected by an oxygen concentrationsensor, an temperature sensor or others, the retard amount Rm isdetermined by the feedback control, and the main injection FM isperformed with these retard amounts Rm.

[0141] In the first method of this second embodiment, the injectionquantity Vp of the pilot injection Fp is calculated from the relationbetween the retard amount Rm and the injection quantity Vp of the pilotinjection Fp, determined preliminarily, by experiment or others, and thepilot injection Fp is performed with this injection quantity Vp as shownin FIGS. 5(b) and 5(c).

[0142] This fuel injection control allows to generate an exhaust gasstate necessary for the catalyst regeneration or others, because themain injection Fm can burn without misfire, even when a large retardamount Rm is adopted, in the main injection Fm.

[0143] Moreover, as this injection quantity Vp of the pilot injection Fpincreases/decreases in correspondence to the retard amount Rm of themain injection Fm, according to a relation determined preliminarily byexperiment or others, the fuel would not be consumed unnecessarily, andthe deterioration of the fuel efficiency can be limited to the minimum.

[0144] Besides, in the second method of the second embodiment, a voltageof about 50 to 200V is applied to a conductive portion facing to theinside of the combustion chamber and separated by an appropriateinterval (for instance, between the glow plug and combustion chamberwall), and an ion gap sensor for detection of electric current flowingin this conductive portion is installed to monitor the fuel combustionstate in the engine combustion chamber.

[0145] Furthermore, the feedback control is realized by taking theoutput (voltage value) of this ion gap sensor as desired value and theinjection quantity Vpc of the pilot injection Fp as control variable.

[0146] There, when the retard amount Rm and the injection quantity ofthe main injection Fm are determined, the main injection Fam isperformed with this retard amount Rm and, at the same time, theinjection quantity Vp of the pilot injection Fp is controlled by thisfeedback control.

[0147] To be more precise, it is so controlled to increase the injectionquantity Vp of the pilot injection Fp when the ion concentration lowersafter the pilot injection Fp and the voltage drop is small, as the fuelof the pilot injection Fp has burned out and the fuel of the pilotinjection Fp becomes hard to ignite and, on the contrary, decrease theinjection quantity Vp of the pilot injection Fp when the ionconcentration is high and the voltage drop is large, as there is enoughfuel of the pilot injection Fp and the fuel. of the main injection Fmcan ignite easily.

[0148] By this fuel injection control through increase/decrease of theinjection quantity Vp of the pilot injection Fp, the injection quantityVp of the pilot injection Fp can be optimized in respect to the retardamount Rm of the main injection Fp of that time, byincreasing/decreasing the pilot injection quantity, through thedetection of misfire occurrence or possibility of misfire.

[0149] In short, it is composed to increase/decrease automatically theinjection quantity Vp of the pilot injection Fp, according to theincrease/decrease of the retard amount Rm of the main injection Fp.

[0150] This fuel injection control allows generating an exhaust gascomposition necessary for the catalyst function, as the main injectionFm can be burned without misfire, even if a large retard amount Rm istaken, in the main injection Fm.

[0151] More specifically, in the case of not increasing the injectionquantity Vp of the pilot injection Fp of the prior art, the misfireoccurred and white smoke was generated with the retard amount Rm of themain injection on the order of about 10° ATDC in crank angle, while inthe present invention, the retard amount Rm of the main injection Fp canbe retarded until 40° ATDC to 50° ATDC in crank angle.

[0152] Further, in the case of the second method using this ion gapsensor, it is unnecessary to determine, previously, the injectionquantity Vp of the pilot injection Fp corresponding to the retard amountRm of the main injection Fp, allowing, also, to burn the fuel of themain injection Fm securely. Moreover, being feedback control, theinjection quantity Vp of the pilot injection Fp can be limited to thestrict minimum, allowing to save more fuel.

[0153] Both in the first method or the second method, the injectionquantity Vp in the pilot injection Fp is increased/decreased incorrespondence to the increase/decrease of the retard amount Rm of themain injection Fp, without changing the timing tp to start the injectionof the pilot injection Fp. By fixing this timing tp of the pilotinjection Fp, the fuel of the pilot injection Fp can be burned securelynear the top dead center where the pressure and the temperature arealways high facilitating the fuel combustion, and the fuel of the maininjection Fm can ignite before the temperature decreases, by securingthe kindling charcoal.

[0154] Third Embodiment

[0155] In the diesel engine fuel injection control method of the thirdembodiment concerning the injection quantity of the pilot injection andthe injection quantity of the main injection, pilot injection Fp andmain injection Fm as shown in FIG. 6(a) are performed during theexecution of the normal pilot injection. The injection quantity of thispilot injection Fp is a prescribed value and, a previously establishedfixed quantity.

[0156] There, the injection quantity of the main injection Fm isincreased/decreased when it becomes necessary to rise the exhaust gastemperature, or, generate temporally an exhaust gas of reductiveatmosphere by lowering the oxygen concentration in the exhaust gas, inorder to rise the catalyst temperature of the exhaust gas post-treatmentapparatus, regenerate NOx occlusion reduction type catalyst, orregenerate the filter by burning and eliminating PM caught by the DPF.

[0157] For this increase/decrease of the injection quantity of the maininjection Fm, in order to make the oxygen concentration in the exhaustgas and the exhaust gas temperature the predetermined desired values,the injection quantity of the main injection Fm is performed by apredetermined injection quantity Vm, or the injection quantity Vm isdetermined through a feed back control by detecting the oxygenconcentration or the exhaust gas temperature by means of an oxidenconcentration sensor, a temperature sensor, or other detection means,thereby performing the main injection Fm with the obtained injectionquantity Vm.

[0158] In the first method according to the third embodiment, similarlyto the first method of the second embodiment, the injection quantity Vpof the pilot injection Fp is calculated from the relation between theinjection quantity Vm and the injection quantity Vp of the pilotinjection Fp, determined preliminarily, by experiment or others, for theinjection quanty Vm of this main injection Fm, and the pilot injectionFp is performed with this injection quantity Vp as shown in FIGS. 6(b)and 6(c), from the normal injection control shown in FIG. 6(a).

[0159] This fuel injection control allows to generate an exhaust gasstate necessary for the catalyst regeneration or others, because themain injection Fm can burn without misfire, even when the injectionquantity Vm is reduced, in the main injection Fm.

[0160] Moreover, as this injection quantity Vp of the pilot injection Fpincreases/decreases in correspondence to the injection quantity Vm ofthe main injection Fm, according to a relation determined preliminarilyby experiment or others, the fuel would not be consumed unnecessarily,and the deterioration of the fuel efficiency can be limited to theminimum.

[0161] Besides, in the case of changing the injection quantity Vp of thepilot injection Fp in accordance with the injection quantity Vm of themain injection Fm also, similarly to the second method of the secondembodiment, the injection quantity Vp of the pilot injection Fp can becontrolled through the feedback control, by using a combustion statedetection means, such as ion gap sensor or others.

[0162] Fourth Embodiment

[0163] Now, the diesel engine fuel injection control method of thefourth embodiment for performing a multistage auxiliary injection beforethe main injection.

[0164] In the composition of this diesel engine fuel injection controlmethod, the engine fuel injection is performed by dividing into the maininjection and the multistage auxiliary injection before the maininjection, as shown in FIG. 7, the injection timing tm of the maininjection Fm is retarded and, at the same time, the injection of theauxiliary injection is performed in multistage of twice or more(three-stage injection in FIG. 7) at a timing before injection timing tmof the main injection Fm.

[0165] First, the initial first auxiliary injection Fs1 is injected andignited at a timing ts1 near the top dead center (TDC) where thepressure and the temperature in the cylinder are high, and permit theignitionability. The fuel injection quantity Vs1 of this first auxiliaryinjection Fs1 shall be low enough not to affect the torque generation.

[0166] The second auxiliary injection Fs2 shall be performed at a timingts2 before the end of combustion of the injected fuel of this firstauxiliary injection Fs1. In this second auxiliary injection Fs2, as thepiston begins to descend, the torque generation is suppressed, even ifmore fuel injection quantity Vs2 than the first auxiliary injection Fs1is injected.

[0167] The third auxiliary injection Fs3 shall be performed at a timingts3 before the end of combustion of the injected fuel of this secondauxiliary injection Fs2. In this third auxiliary injection Fs3, thetorque generation is suppressed, even if further more fuel injectionquantity Vs3 than the fuel injection quantity Vs2 of the secondauxiliary injection Fs2 is injected.

[0168] There, the ignitionability is secured by the first injection Fs1of these auxiliary injections, and the combustion flame is sustaineduntil the injection timing tm of the main injection Fm, by the secondand following injections Fs2, Fs3, allowing to burn securely even with alargely retarded main injection Fm.

[0169] Consequently, white smoke or misfire do not occur, and exhausttemperature can be risen considerably, because the main injection Fm canbe ignited securely, even when the main injection Fm is largelyretarded, through the sustainment of the combustion flame by thisplurality of auxiliary injections Fsi.

[0170] As a result, it becomes possible to rise the exhaust temperaturekeeping the generated torque low, and an exhaust temperature necessaryfor PM regeneration comes to be secured even under a low load, by thisengine fuel injection control method.

[0171] Though in the example of FIG. 7, the number of time of auxiliaryinjection Fsi is et to 3, and the quantity is increased gradually fromthe fist fuel injection quantity Vs1 to the third fuel injectionquantity Vs3, passing through the second fuel injection quantity Vs2,the number of injection can be increased by setting the fuel injectionquantity Vsi of respective auxiliary injection Fsi equal as anotherexample shown in FIG. 8. Also, although not shown, several auxiliaryinjections may be injection with a same fuel injection quantity, andthereafter, the auxiliary injection can be performed with a increasedfuel injection quantity.

[0172] Now, hereinafter, the regeneration control method of exhaust gaspost-treatment apparatus of an embodiment according to the presentinvention shall be described taking continuous regeneration type dieselparticulate filter system (continuous regeneration type DPF system,hereinafter), referring to drawings. This regeneration control method ofcontinuous regeneration type DPF system is a regeneration control methodusing the aforementioned fuel injection control method.

[0173]FIG. 9 shows the composition of this continuous regeneration typeDPF system 1. This continuous regeneration type DPF system 1 comprises afilter with catalyst (filter) 3 installed in an exhaust passage 2 of anengine E, and a regeneration control means 40.

[0174] This filter with catalyst 3 is formed with a monolith honeycombform wall flow type filter in which inlets and outlets of channels of aporous ceramic honeycomb are in stagger stopped up alternately, and aporous catalyst coat layer 31 carrying a catalyst 32 is disposed on aporous wall face 30 of this filter 3.

[0175] This catalyst 32 is composed of a precious metal oxidationcatalyst 32A such as platinum (pt), palladium (Pd), copper (Cu), and aPM oxidation catalyst 32B such as cerium dioxide (CeO₂) presenting anoxidation activity in respect to HC, CO and PM.

[0176] Besides, a regeneration control means 40 is, normally, includedin a control unit (ECU: engine control unit) 50 for controlling theengine E operation in general, inputs the output from a DPF inletexhaust gas temperature sensor 51 on the exhaust inlet side of thefilter with catalyst 3 and a DPF differential pressure sensor 52 fordetecting the differential pressure before and after the filter withcatalyst 3, for controlling the regeneration of the filter with catalyst3.

[0177] Now, the regeneration control method in the continuousregeneration type DPF system 1 of the aforementioned composition.

[0178] This regeneration control method is performed according to theregeneration control flow as illustrated in FIG. 11. For the facility ofthe explanation, these illustrated flows are shown as flows to be calledrepeatedly and executed, in parallel with the control flow of the engineE.

[0179] In short, this flow is called repeatedly and executed after acertain time, in parallel during the operation control of the engine Eand, when the control of the engine E is terminated, this flow will notbe called no more, and this filter regeneration control terminatessubstantially.

[0180] In the regeneration control flow of the present invention, asshown in FIG. 11, in the step S10, the judgment of regeneration start isperformed by checking the clogging of filter by PM accumulationestimated value PMs, and when this PM accumulation estimated value PMsexceeds a predetermined judgment value PMsmax, in the step S20, thefilter with catalyst 3 is regenerated by the regeneration A modeoperation or regeneration B mode operation.

[0181] First, when this regeneration flow starts, in step S10, theregeneration start is judged and in step S11, PM trap value PMt iscomputed. This PM trap value PMt is calculated from the differencebetween PM exhaust quantity and PM purification quantity computed fromthe map data of previously input PM exhaust map or others, based ontorque Q and engine speed Ne showing the engine E operation state, DPFinlet exhaust gas temperature Te measured by DPF inlet exhaust gastemperature sensor 51, or others.

[0182] Or, PM deposit quantity PMt caught by the filter with catalyst 3is computed from the comparison between DPF loss differential pressuredetected by a DPF differential pressure sensor 52, and previously inputDPF differential map.

[0183] Then, in the following step S12, PM accumulation estimated valuePMs is computed by accumulation calculation considering the time of thisPM deposit quantity PMt.

[0184] In the judgment of this step S13, the necessity or not to startthe regeneration mode operation is judged based on the determinationthat the PM accumulation estimated value PMs exceeds or not apredetermined judgment value PMsmax. In this judgment, if it is judgednecessary to start the regeneration mode operation, it proceeds to theregeneration mode operation of the step S20, and if it is judgedunnecessary to start the regeneration mode operation, it returns as itis.

[0185] The regeneration mode operation of the step S20 is performed asfollows.

[0186] First, in the step S21, DPF inlet exhaust gas temperature Te ischecked, and it is judged if the temperature Te is superior or not to apredetermined exhaust gas temperature Te1.

[0187] In this step S21, if the DPF inlet exhaust gas temperature Te isa temperature inferior to the predetermined exhaust gas temperature Te1(for instance, about 350° C.), namely, equal or inferior to a lowtemperature oxidation area, the regeneration A mode operation of thestep S22 shall be performed.

[0188] In the present invention, as the exhaust gas temperature is risenby performing any one of the aforementioned fuel injection control (fuelinjection control involving a multistage auxiliary injection in FIG.11), during the regeneration A mode operation in this low temperaturearea, PM can be oxidized and eliminated.

[0189] Then, returning to the step S21, the step S22 and the step 21 arerepeated until the DPF inlet exhaust gas temperature Te exceeds thepredetermined exhaust gas temperature Te1.

[0190] In this step S21, in case where the DPF inlet exhaust gastemperature Te becomes higher than the predetermined exhaust gastemperature Te1, or in case where it is higher from the beginning, theregeneration B mode is performed in the step S23.

[0191] In this regeneration mode operation, PM is oxidized andeliminated, by a fuel injection control appropriate for respectivetemperature, because the exhaust gas temperature is equal or superior tothe low temperature oxidation area (for instance, equal or superior to400° C.), namely, equal or superior to a temperature where PM can beoxidized by oxidation catalyst, PM oxidation catalyst, or directcombustion.

[0192] And, in case where the exhaust gas temperature Te is in a lowtemperature oxidation temperature area (about 350° C. to 450° C.), NO isoxidized to NO₂ by an oxidation catalyst 32A, and PM can be oxidized andeliminated with this NO₂.

[0193] On the other hand, in case where the exhaust gas temperature Teis in a medium temperature oxidation area (about 400° C. to 600° C.), asPM can be oxidized and eliminated by O₂ in the exhaust gas, with PMoxidation catalyst, the engine operation is controlled to maintain theexhaust gas temperature to the medium temperature oxidation area ormore, and PM caught in the filter with catalyst 3 is oxidized andeliminated by O₂ in the exhaust gas, with PM oxidation catalyst 32B.

[0194] Then, when the exhaust temperature Te is in a high temperatureoxidation area (for instance, equal or superior to 600° C.), PM burnsdirectly with O₂ in the exhaust gas.

[0195] There, this regeneration B mode operation is performed, and it isjudged if the exhaust gas pressure Pe becomes or not smaller than thepredetermined exhaust gas pressure value Pe1, to check if the filterregeneration has terminated or not.

[0196] In case where the filter regeneration has not terminated, itreturns to the step S23 and the regeneration B mode operation issustained, and in case where the filter regeneration has terminated, theregeneration mode operation is terminated and, in the step S25, the fuelinjection is reset to the original injection mode, the PM accumulationestimated value PMs is reset (PMs=0), or other regeneration modetermination operation is completed, before return.

[0197] The use of the aforementioned regeneration control method permitsthe oxidation and elimination of PM caught and accumulated in thefilter, by rising the exhaust gas temperature, through any one of theaforementioned fuel injection controls of the present invention such asfuel injection control involving a multistage auxiliary injection in theregeneration A mode operation or others, even if the filter regenerationcomes to be required in an engine operation state at a low exhausttemperature, such as idling operation or extremely low load operation.

[0198] Further, the exhaust temperature can be risen keeping the enginespeed and torque in the normal engine operation, so the engine torquevariation can be controlled.

[0199] Though the continuous regeneration type DPF system shown in FIG.9 is taken and described as an example of continuous regeneration typeDPF system, the regeneration control method of the continuousregeneration type DPF system of the present invention can also beapplied to the continuous regeneration type DPF system shown in FIG. 15to FIG. 17, and the continuous regeneration type DPF system of thepresent invention is not limited to the continuous regeneration type DPFsystem shown in FIG. 9.

EXAMPLE

[0200] An example of fuel injection control involving a multistageauxiliary injection of the fourth embodiment of the present invention isshown in FIG. 12, while a comparative example of fuel injection controlinvolving a pilot injection of the prior art is shown in FIG. 13. Itshould be appreciated that the engine operation condition at that time,is 1,000 rpm in engine speed, under no load.

[0201] In the example of fuel injection control involving a multistageauxiliary injection shown in FIG. 12, the first auxiliary injection(injection quantity=2.0 mm³/st) is performed at 8° ATDC, the secondauxiliary injection (injection quantity=3.5 mm³/st) at 20° ATDC, and themain injection (injection quantity=4.6 mm³/st) at 33° ATDC, to obtain ainlet exhaust gas temperature of 350° C. and an exit exhaust gastemperature of 410° C. in the DPF apparatus.

[0202] On the other hand, in the comparative example of fuel injectioncontrol involving a pilot injection shown in FIG. 13, the pilotinjection (1.5 mm³/st) is performed at the top dead center (TDC) and themain injection (14.8 mm³/st) at 23° ATDC, to obtain a inlet exhaust gastemperature of 101° C. and an exit exhaust gas temperature of 96° C.

[0203] Therefore, it can be known that the exhaust gas temperature canbe risen by 200° C. or more compared to the case of fuel injectioncontrol involving a pilot injection, by adopting the fuel injectioncontrol involving a multistage auxiliary injection.

[0204] It should be appreciated that the ignitionability is stillpossible even when the first auxiliary injection timing (ts1) is set to8° ATDC compared to the injection timing tp (0° ATDC) of the pilotinjection, because the main injection can ignite and burn securely, bythis plurality of auxiliary injection (Fsi) and, therefore, thetemperature in the cylinder is high in the following cycle.

INDUSTRIAL APPLICABILITY

[0205] In the diesel engine fuel injection control of a vehicle or thelike, while temporally controlling the fluctuation of the torque output,it is an object of the present invention to realize at least one of therise of exhaust gas temperature and the reduction of oxygenconcentration in the exhaust gas, by the fuel injection temporal controlof the main injection/after injection, the main injection/sub and mainafter injection, the pilot injection/the main injection retard, themultistage auxiliary injection/main injection retard, or the like.

[0206] The regeneration control method of exhaust gas post-treatmentapparatus using this fuel injection control can heat and activateoxidation catalyst or NOx catalyst, by rising the exhaust gastemperature, regenerate the filter by burning PM caught in the filter ofa DPF apparatus for catching PM, or regenerate occlusion substance ofNOx occlusion reduction type catalyst, by lowering the oxygenconcentration in the exhaust gas, during the regeneration treatment inthe exhaust gas post-treatment apparatus of a diesel engine.

[0207] Especially, in the continuous regeneration type DPF system, andwhile controlling the torque variation, it becomes possible to rise theexhaust gas temperature considerably, and regenerate the filter, even inan engine operation state at a low exhaust gas temperature, such asidling operation or extremely low load operation, making the filterclogging easily and making the filter regeneration difficult.

[0208] Consequently, the regeneration treatment of exhaust gaspost-treatment apparatus for eliminating NOx, PM or others emitted fromthe diesel engine loaded on a vehicle such as automobile, lorry, orothers can be performed efficiently, by controlling the deterioration ofthe fuel efficiency, without deteriorating the comfort of riding.

[0209] Therefore, it becomes possible to eliminate with a highpurification rate NOx, PM or others emitted from an automobile, lorry,or others, and prevent from air pollution.

What is claimed is:
 1. A diesel engine fuel injection control method forperforming an after injection after a main injection for at least one ofrising of diesel engine exhaust gas temperature and decrease of theoxygen concentration in the exhaust gas, wherein said after injection isperformed in a range of 40° ATDC to 90° ATDC of a crank angle.
 2. Thediesel engine fuel injection control method of claim 1, wherein saidafter injection is performed by a multistage injection of sub afterinjection and main after injection and, at the same time, said sub afterinjection is performed in a range of 40° ATDC to 70° ATDC of the crankangle and said main after injection in a range of 70° ATDC to 90° ATDCof the crank angle.
 3. The diesel engine fuel injection control methodof claim 2, wherein said main after injection is performed bycalculating the injection quantity and the injection timing of said mainafter injection according to the relation of the injection quantity andthe injection timing of said main after injection in respectiveoperation states of an engine, determined previously.
 4. The dieselengine fuel injection control method of claim 2, wherein said sub afterinjection is performed by calculating the injection quantity and theinjection timing of said sub after injection according to the relationof the injection quantity and the injection timing of said sub afterinjection in respective operation states of an engine, determinedpreviously.
 5. The diesel engine fuel injection control method of claim3, wherein said sub after injection is performed by calculating theinjection quantity and the injection timing of said sub after injectionaccording to the relation of the injection quantity and the injectiontiming of said sub after injection in respective operation states of anengine, determined previously.
 6. The diesel engine fuel injectioncontrol method of claim 2, wherein it is determined whether to performor not said sub after injection, based on the output values of a fuelcombustion state detection means, all the way monitoring the fuelcombustion state in an engine combustion chamber by the fuel combustionstate detection means, and said sub after injection is performed basedon said determination.
 7. The diesel engine fuel injection controlmethod of claim 3, wherein it is determined whether to perform or notsaid sub after injection, based on the output values of a fuelcombustion state detection means, all the way monitoring the fuelcombustion state in an engine combustion chamber by the fuel combustionstate detection means, and said sub after injection is performed basedon said determination.
 8. The diesel engine fuel injection controlmethod of any one of claim 2, 3, 6 or 7, wherein at least one ofinjection quantity and injection timing of said sub after injection isadjusted and controlled, based on the output values of a fuel combustionstate detection means, all the way monitoring the fuel combustion statein the engine combustion chamber by the fuel combustion state detectionmeans.
 9. An diesel engine fuel injection control method for performinga pilot injection and a main injection by controlling the fuel injectionof a diesel engine, and for performing at least one engine fuelcombustion among retard of said main injection or increase/decrease ofthe injection quantity, for at least one of rising of diesel engineexhaust gas temperature and decrease of the oxygen concentration in theexhaust gas, wherein the injection quantity of said pilot injection isincreased/decreased, in accordance with the increase/decrease at leastone of retard amount and injection quantity of said main injection. 10.The engine fuel injection control method of claim 9, wherein saidinjection quantity of said pilot injection is calculated in accordancewith the relation between at leas one quantity among said retard amountor said injection quantity of said main injection obtained previouslyand said injection quantity of said pilot injection.
 11. The engine fuelinjection control method of claim 9, wherein said injection quantity ofsaid pilot injection is increased/decreased based on the output value ofa fuel combustion state detection means, all the way monitoring the fuelcombustion state in the cylinder by the fuel combustion state detectionmeans, when at least one of said retard amount and said injectionquantity of said main injection shall be increased/decreased.
 12. Adiesel engine fuel injection control method, composed to retard theinjection timing of a main injection and, at the same time, perform theauxiliary injection twice or more at a timing before an injection timingof the main injection, in order to rise an exhaust temperature of adiesel engine.
 13. The diesel engine fuel injection control method ofclaim 12, wherein the injection timing of said main injection is set to25° ATDC to 45° ATDC.
 14. The diesel engine fuel injection controlmethod of claim 12, wherein the fuel injection quantity of the auxiliaryinjection of later injection timing is increased more than the fuelinjection quantity of the auxiliary injection of earlier injectiontiming.
 15. The diesel engine fuel injection control method of claim 13,wherein the fuel injection quantity of the auxiliary injection of laterinjection timing is increased more than the fuel injection quantity ofthe auxiliary injection of earlier injection timing.
 16. Theregeneration control method of exhaust gas post-treatment apparatus,including the diesel engine fuel injection control method of any one ofclaims 1 to 7 and 9 to 15, for the regeneration control to be performedfor regeneration treatment of an exhaust gas post-treatment apparatus,in the exhaust gas post-treatment apparatus for excluding hazardousconstituent in the engine exhaust gas.
 17. The regeneration controlmethod of exhaust gas post-treatment apparatus of claim 16, wherein saidexhaust gas post-treatment apparatus is a continuous regeneration typediesel particulate filter system provided with a filter for catchingparticulate member in the engine exhaust gas, and oxidizing andeliminating the caught particulate a catalytic function.